A study will be made of the role played by J chain in the transport of polymeric immunoglobulins into external secretions, as well as its function in the distribution of cells that produce polymeric immunoglobulins. Phylogenetic development of J chain will be studied in sera and secretions of fresh-water fish. J chain of humans and fresh water fish will be chemically compared. Ontogenetic development in human, mouse, and baboon body fluids and tissues will be investigated. Cellular distribution, immunoglobulin association, and significance of J chain under various pathologic conditions will be determined in patients with multiple myelomatosis and inflammatory diseases of gastrointestinal tract. J chain synthesis during cellular differentiation and immune response will be studied in human and animal lymphoid cells after stimulation with mitogens, antigens, and glandular extracts. The pattern of organ localization of cells that produce immunoglobulins and J chain will be studied in relation to the route of immunization. Immunochemical, immunohistochemical, and electrophoretic methods will be used. BIBLIOGRAPHIC REFERENCES: Mestecky, J., Kulhavy, R., Schrohenloher, R. E., Tomana, M. and Wright, G.P. Identification and Properties of J. Chain Isolated from Catfish Macroglobulin. J. Immunol. 115, 993-997, 1975. Radl, J., Swart, A.C.W. and Mestecky, J. The Nature of the Polymeric Serum IgA in Man. Proc. Soc. Exptl. Biol. & Med. 150, 482-484, 1975.